Thermometer



June 23, 1931. H. Y. NORWOOD 1,811,184

THERMOMETER Filed Feb. 26, 1930 2 Sheets-Sheet l INVENTORI ATTORNE June 23, 1931. NORWOOD 1,811,184

THERMOMETER Filed; Feb. 26, 1930 2 Sheets-Sheet 2 INVENTOR A TORNEY Patented June 23, 1931 UNITED STATES PATENT OFFICE HARRY Y. NORWOOD, OF WEST RUSH, NEW YORK, ASSIGNOR TO TAYLOR INSTRUMENT COMPANIES, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK THERMOMETER Application filed February 26, 1930. Serial No. 431,443.

This invention relates to thermometers and,

more in particular to a method of making thermometer tubing. In its preferred application the invention has to do with tubing of elliptical or semi-elliptical cross-section.

According to the Patents 222,420 and Re. 10,189, a very large magnification of the bore and the mercury column may be obtained by having the bore disposed farther back of the lens front than the mechanical center of the tube. In fact, ithas been found that a maximum magnification can be obtained by making the tube of elliptical crosssection and placing the bore into one of the foci thereof. \Vhen viewing the thermometer thus constructed through the curvature most remote from the bore, the visual width of the column of mercury or other liquid extends across the whole width of the tube so that the liquid appears to transversely fill the whole tube.

Heretofore apparently no attempt has been made to produce a tubing of small bore wherein the bore is disposed at one of the foci of an ellipse and the reason for that is probably the following:

In the first instance, the method used in making the regular thermometer tubing in which the bore is approximately located in the center. cannot be used because there is no way of locating the bore with certainty at one of the foci of an ellipse. The only available method of forming a tube of a definite cross-section and placing the bore at a definite point therein, is to place a mass of glass into a mould of the required crosssectional"configuration, then forcing a metal rod into the mass of glass in the mould, then applying the blowpipe, or, in fact, any other piece of metal rod or tube by which the ball of glass may be pulled out of the mould and suspended for the drawing operation, and then taking the glass out of the mould together with the blow pipe and drawing the tubing in the usual way.

This method, however, has heretofore not been a success because great care must be exercised lest the metal rod adheres to the hot glass. The rod must be moved through the body of the glass long enough to slightly chill the surface of the bore formed by the I rod and to wipe the surface to well define the bore so as to make it the equivalent of a blown bore.

lVhile the relatively large rod may at times be successfully employed for this purpose, this method is not available for producing thermometers of smaller bores. A rod for forming the initial bore in the mass of hot glass to be drawn, must be of such small diameter that even the shortest stab into and. out of the hot glass would cause a heating up of the rod to such an extent as to cause it to stick in the glass.

The general object of the present invention is a method of producing small-bore thermometer tubing wherein the bore is disposed in" a definite relation to the cross-sectional area of the tubing.

A more specific object is a method of producing thermometer tubing having an elliptical or semi-elliptical cross-section, wherein the here is disposed in one of the foci of the ellipse.

/ The principal object of the invention is a clinical thermometer or a thermometer having a small bore of the order of clinical -thermometer bores, wherein the cross-section of the tubing is elliptical or semi-elliptical and the here is disposed in one of the foci of the ellipse.

The invention, the underlying principle of operation, the effect and the advantages derived from it and its technical and commercial importance may be more fully understood from the accompanying drawings wherein Fig. 1 is an elevation of a thermometer embodying the invention;

Fig. 2 is a cross-section thereof on a larger sca e;

Fig. 3 is a sectional view of an arrangein connection with the mould shown in Figs. 4 and 5. j

Fig. 8 is a perspective view of the arrangement shown in Fig. 3;

Fig. 9 is a plan view of another mould used in the process of the invention;

10 is a cross-section taken on line 1010, together with other parts showing its application Fig. 1 is a cross-section of an arrangement representing a modification in the process of the invention;

Fig. 12 is a cross-section of a mould used in said modification; and

Fig. 13 is a sectional view of a detail showing another modification.

l'laving'reference to Fig. 2, 1 is a stem containing the bore 2. The surface line 8 of the stem below the line aa in Fig. 2, i. e. the surface presented to the eye of the observer, is part of an ellipse, and the bore 2 is located in that focus of the ellipse which is remote from the front surface 8. Since the part of the ellipse behind the bore is of no consequence, it may be omitted. Only so much of the glass is necessary as to place the bore within it.

The principal feature of the process of producing a tubing according to the invention, is the making of the tube of two separate parts of glass joined to each other in the direction of the bore and preferably in such a way as to form the bore.

Having reference to Fig. 3, 3 represents a ball of glass preformed in a suitable mould similar to that shown in Fig. 12, to have in part an elliptical cross-section such that one focus lies entirely within its area and the second focus lies at the periphery. It is the location of this second focus which is of importance. .In the drawings, the surface line i below the line 7)?) in Fig. 3, is substantially elliptical and the second focus lies at.- the upper or rear surface of the ball 3.

To this upper or rear surface of the ball is applied a strip of glass i having in its contact surface a groove The strip et and the ball 3 are joined, of course, while both are in a plastic condition.

The strip 4: is preformed in a mould G which is entirely open on one side, like an open box, and has in one of the four confining walls a slot 7 so that a rod may be entered at the free end of the wall and moved bodily down to the bottom of the mould at right angle to the latter or parallel to the walls adjoining the slotted wall.

In practice, a gob of glass is gathered on a rod 8 and is then placed into the mould with the rod 8 extending out through the slot 7. A forming plunger 9 is then pressed down upon the glass. The bottom of the mould is preferably curved convexly and is provided with a central rib 10 to form in the glass the groove 5. Then the piece of glass 4 thus formed is taken out of the mould and, if necessary, reheated, and when both the ball of glass 3 and the piece of glass 4 are in a proper condition for joining, the strip of glass 4 is placed upon the ball, as indicated in F ig. 8 with the groove'facing the surface of the ball. Then the lateral portions of the strip is are wiped down outwardly from the center containing the groove so as to squeeze out all air to avoid air pockets or secondary bores.

Vihen the union is completed, the body of glass, which has the configuration of Fig. 2, is drawn down to the required size. It is understood that while Figs. 2 and 3 are of approximately like size, the ball shown in Fig. 3 on a relatively small scale, represents a ball of glass about 56 in diameter, while the tubing shown "in Fig. 2 on a relatively large scale, represents a thermometer tubing, the tubing retaining of course, the crosssectional configuration of the ball of glass at the time of the drawing operation.

\Vhen the linished tubing is filled with mercury, the latter appears to transversely fill the tube from side to side, as indicated in Fig. 1 wherein 12 represents the mercury column and the space above the column is transparent. In order to emphasize the contrast between the mercury column and the space above the same, I propose to apply whit-e enamel. This may be conveniently done by adding a layer of enamel to the ball of hot glass after the strip 4 is joined, such layer 13 being shown in Fig. 2. This layer 13, as it is disposed only a very short distance behind the bore, which is at the focus of the ellipse. and is considerably wider than the bore, appears across the full width of the tube above the mercury column and thus stands out in a maximum contrast to the dark mercury column.

To properly locate the groove 5. I preferably place the hot preformed ball 3 into a mould 1-i shaped in cross-section so as to receive the ball in one definite position and then place the hot strip t in vm1netrical' position thereon. To this end, the mould preferably contains guide arms 15 pivotally carried on studs 16 and the arms 1:"), at their free ends, carry abutment plates 17 for definitely positioning the strip in lateral direction so that when the strip 4 is placed between the plates, the groove 5 lies in the tocus of the ellipse throughout the length of the ball of glass and consequently when the glass is drawn, the bore of the tube will always he at the focus of the ellipse as intended.

The studs are preferably pivoted at their lower ends and are held in a normal upright position by springs 18. After the strip 1 has been placed into position. the. arms can be readih withdrawn and the ball can be easily taken out of the mould.

The arrangement in Fig. 11 shOws a slight modification from the arrangement deg scribed. The groove 21. is provided in the ball 20 and the strip of glass 22 serves as the closure for the groove to define the bore. To carry out this construction, the mould :24 is provided with a rib similar to the rib 10 in Fig. The mould 2% thus not only shapes the ball of glass to give it a partly elliptical shape in cross-section, as previously explained, but at the same time forms the groove 21. The treatment of the ball 20 and the strip is otherwise the same as described.

Having reference to Fig. 13, the glass strip 26 may be provided with a groove 27 for receiving a colored enamel. The position of the groove 27, after the strip 26 is joined to the ball, is so close to the bore that in the tubing drawn from it, the groove 27 is almost at the focus. However, the groove may be made slightly wider than the bore to make up for the difference in the location.

In the foregoing I have attempted to describe only the broader aspect of the invention and one particular method of carrying it into client. It is understood that other methods and other auxiliary apparatus may be resorted to for accomplishing the object of the invention.

The principal advantage of a thermometer tubing according to the invention is, as pre viously suggested, the optical efi'ect whereby the mercury column, which is ordinarily not readily discernible, at least not in thermometers of very small bore, such as clinical thermometers, is magnified to a maximum and, in fact, visually occupies the whole stem from side to side.

Another very material advantage is the disposition of the white or colored layer immediately to the rear of the bore. By this disposition the light or color effect, as the case may be, is so close to the bore that the back ground thus produced has a maximum contrast effect and in addition visually appears in the same vertical plane as tl- 3 mercury column. The reduction of -the thickness of glass between the bore and the rear surface of the tube to anegligiblequantity, as this may be accomplished particularly in the form shown in Fig. 11, is instrumental in effecting a maximum of contrast between the mercury column and the enamel backgrdund.

In addition, the amount ofenamel for the colored member may be very small since the width of it need not materially exceed that of the bore. The advantage of this feature is the elimination or at least material reduction of such strains in the glass stem as are due to the well known differential action of glass and enamel as to expansion and contraction.

\Vhile the cross-section of thermometers according to the invention is not strictly elliptical. it differs from an elliptical cross-section only in some comparatively small detail.

,"For the sake of simplicity of expression, the

"terms elliptic space and elliptical cross-' section have been employed in a general way and not in the strict sense.

I claim:

1. In a process of making thermometer tubing, the steps which consist in forming a body of glassin a mould so as to define in one surface thereof a groove, joining thereto while in plastic condition another piece of glass to form a cover for said groove and then drawing the resulting body of glass.

2. In a process of making thermometer tubing. the steps of forming a bore, which consist in forming a groove-forming rib on the surface of a relatively large body of metal, pressing a body of glass in plastic condition against the said surface, joining thereto while in plastic condition another piece of glass to form acover for said .Iroove and then drawing the resulting body of glass.

In testimony whereof I atfix my signature.

HARRY Y. NORWOOD. 

